Guest Blog by Bruce Tolley, VP Marketing Solarflare Communications
Last week, I attended the Ethernet Alliance's first Technology Exploration Forum which was ably moderated by John D'Ambrosia, a Force10 employee and chair of the IEEE 802.3 40/100G task force (also known as IEEE P802.3ba). The day started with a key note by by David Law of 3Com, currently Chairman of the IEEE 802.3 Working Group. Mr. Law gave an excellent historical and standards perspective on Ethernet, observed that the 40/100G is standardizing no fewer than eight physical layers to cover various applications of 40G and 100G including 1 meter backplane connections, discussed how the Ethernet group needs a supermajority of 75% of the votes to achieve consensus on technical issues, and outlined current standards work defining converged Ethernet such as data center bridging.
IEEE 802.3 is the standards development organization (SDO) that first standardized Ethernet in the 1980s following up on the pioneering specmanship work of Digital Electronics, Intel and Xerox (the so-called DIX document).
Although the ink is not yet dry on the 40/100G spec, many of the sessions sounded like preliminary versions of what IEEE 802.3 committee calls “calls for interest” on 25 G serial for backplanes and 40G serial on duplex fiber for network interconnect. Looking even further into the future, Chris Cole, an engineer with Finisar, presented his ideas on 400G optical interfaces for another yet to be started Ethernet standard.
Rising above Layer 1 PHY issues, there were noteworthy presentations by IT professionals designing and operating real networks at Facebook and Google, just to name two. Both Facebook and Google today are installing servers that attach at PCIe gen 1 and gen 2 speeds of up to 20Gbps bidirectionally. The need to aggregate and switch thousands of 20Gbps attached network servers increases the pressure for a higher capacity switching fabric.
Donn Lee, a network engineer for Facebook (Palo Alto, Calif.), said his company's rapidly expanding network could use multiple 100G Ethernet systems today if he could get his hands on them. The standard is in a late stage of being finalized by the IEEE 802.3ba group. Facebook is building server clusters to support the estimated 300 million Facebook users. Mr. Lee reported that his bandwidth requirements for the network in Facebook's data centers more than double every year. Lee said his company has considered building its own Ethernet switches while it waits for vendors to deliver switches that go beyond today's 400G switching capacity. Both the presenter from Facebook and from Google expressed desire for network interfaces at speeds greater than 100G. Deutsche Telekom agreed that bandwidth needs are growing and called for a terabit Ethernet effort to start soon.
By show of hands, about a third of those attending the meeting said they would support work on a 400G Ethernet standard. While the Google architect showed how he was using fat trees to build capacity into his network, there was no technical presentation by a systems OEM on the ability to build multi terabit-switches that could support multiple 400G links in the foreseeable future
In addition to the exploration of higher speed technologies, Mike Bennett, chair of the Energy Efficient Ethernet task force, discussed protocols for energy efficiency. The IEEE 802.3 group is soon to publish a protocol that enables 100BASE-T, 1000BASE-T, and 10GBASE-T Ethernet switches and NICs to signal when they have little or no traffic on the wire and drop into a state that consumes substantially less power. I’ll report on that in a future post.
